A known robot control unit controls an assembly robot configured to insert a shaft part fixed to a fixing part into a hole part held by a robotic arm (refer to Japanese Unexamined Patent Application, Publication No. 2008-221387, for example). This robot control unit detects a force applied to the hole part in the insertion direction when a tip end portion of the shaft part contacts a peripheral part of a hole of the hole part, and a moment about an axis line orthogonal to the insertion direction, and performs calculation based on the detected force and moment. The robot control unit uses a result of this calculation to calculate the position of contact between the tip end portion of the shaft part and the peripheral part of the hole with respect to the center of the hole, in other words, the direction and distance of the position of contact with respect to the center of the hole. Then, the robot control unit tries appropriate insertion of the shaft part into the hole part by moving the hole part or the shaft part in accordance with the calculated direction and distance.
Another known assembly robot includes a force sensor, a robotic arm configured to relatively move a first work and a second work, a work grasping unit provided at a tip end of the robotic arm, and a robot control unit configured to control the robotic arm and the grasping unit (refer to Japanese Unexamined Patent Application, Publication No. 2015-168017, for example).
This robot control unit determines whether the first work and the second work are relatively moved based on a value detected by the force sensor, an allowable range of the value, and information about the position of the grasping unit predetermined in accordance with the posture of the robotic arm. The robot control unit determines that the first work and the second work are successfully fitted when the grasping unit moves to a predetermined position.
Another known assembly robot includes a robotic arm configured to fit a second work to a first work, a camera for detecting a positional relation between the first work and the second work, and a detection means configured to detect force or sound received by the robotic arm from the works during a fitting operation (refer to Japanese Unexamined Patent Application, Publication No. 2014-188641, for example). A robot control unit for this assembly robot stores a reference graph of the generated force or sound received by the robotic arm from the works when the fitting operation is successful. The robot control unit determines whether the fitting operation is performed based on a result of the detection by the camera, and determines whether the fitting operation is successful by comparing the reference graph with temporal change of the force or sound detected by the detection means.